Yes they are very bad a lot of the time, but you have to quickly contact them to push them to take action to fix any issues you are having,it can take up a lot of your time & it’s frustrating for sure

Simple.

Don't use Sendle. Especially as they are a broker NOT a courier.

Or any courier, frankly, unless your items are too big for AP.

eBay shipping options (from memory - I stopped using eBay labels when they stopped passing on the massive discounts their volume would get from AP) have several options. Just because Sendle is the first one doesn't mean you have to use it. Except that it is, on the surface, cheaper. But not, as you have found.

So as a seller, you know they have a bad record of service

And you know they are 'very bad a lot of the time'

BUT

You choose to use them, knowing this.......because eBay list them as an option 

Makes a whole lot of sense 

You have some interesting items.

Your postage section says - Ebay postage labels - Standard parcel postage.  If you are using Sendle, please mention that in your listing.  There are many, many people who are not interested in courier deliveries.  AP are easy to get around but not so couriers/brokers

$$, sandy, $$

I don't use Sendle so have no experience but wondered where you are getting your service record for them. Most review sites will show Aust Post as having a lower rating. Where I have a storage unit the office is a drop off point and they have had no issues with them. 

I don't use Sendle so have no experience but wondered where you are getting your service record for them

From the bumper complaining about Sendle, but using them regardless. Presumably because they are cheaper, and undoubtedly the savings aren't passed on to the buyer.

As you don't use Sendle you would naturally not have had issues with them